1. Field of the Invention
The present invention relates generally to plastic bag and film products made from a unique starch-based resin derived from a starch-based feed stock, a compact reactor, and related processes and methods of manufacture. More specifically it relates to film and starch-based film and bag products that have unique degradation properties, which properties may include time-sensitive degradation qualities.
2. Background Art
It is commonly understood that typical plastic films, such as polyethylene, have a long degradation process, as long as 1000 years when buried in the ground. With the launch of the plastic grocery sack, many environmental concerns surfaced about this long degradation process. One approach to overcome this was the introduction of solar degradable grocery sacks that degraded rapidly in sunlight. For example the Solar Sack™ manufactured in 1989 by Polytec Packaging Systems had an expedited solar degradation time of as little as three to six months depending on the latitude, the season, and the amount of sun exposure. However, over time it was deemed that solar degradability was not a satisfactory environmental answer in most applications and to the many suppliers and sellers and users of products made of polyethylene.
Starch-based film and bag products were introduced in the early 1990's and by the late 1990's became commonly used in various industries to provide plastics with degradable properties, whether that is biodegradable, compostable, or otherwise. Since the late 1990's starch-based films having biodegradable properties became commonly used in certain applications such as with mulch bags, whereas it is desirable to have the film degrade rapidly along with its compostable contents. For example, the content of a mulch bag may include compostable grass clippings, leaves, foodstuffs, certain organic wastes, and so on. Obviously the contents would be those that ideally heat up rather quickly in order to convert to mulch.
This particular use of degradable mulch bags is commonly used in several principalities throughout the United States, such as those in the Midwest, Illinois, Wisconsin, and Indiana. Likewise they are sold retail, such as the BioBag™, which claims it composts in a controlled environment in 10 to 45 days. The most common starch-based polymer used for this type of mulch bag and the like is corn.
A more recent emerging trend based on social responsibility is the use of degradable films in packaging bags, whether for carry-out bags in stores, or for retail packaging, which bags are considered inevitably targeted for disposal in landfills. This social responsibility has taken on various forms in various states and certain laws have been mandated to adopt this new emerging trend. For example, in California packaging products used for padding and loose filler in cartons and bags for shipping goods, must be degradable. A report by Time magazine estimates that less than 1% of retail bags are ever recycled.
Today a myriad of companies and states trying to address the emerging degradability issues with carry-out bags, retail packaging, and so on, have instituted various requirements and specifications for degradability, all of which include the use of starch-based resins in one form or another, and many of which are inadequate for addressing the real issue of degradability. For example, BASF produces a resin under its trade name EcoFlex™. It is an aromatic-aliphatic co-polyester. It is made by polymerizing two different molecular structures, an aromatic with natural properties of being too “springy/spongy” so it is co-polymerized with aliphatic to give it some strength. They are a partially cross-linked polymer. It tends to degrade well because the energy stored in the aromatics is triggered by lower-energy-state enzymes by common bacteria. The biggest problem with the Eco-Flex resins is that it is not made from a renewable base material. Renewability is becoming an increasingly important issue environmentally and an important requirement in consumer applications. Another problem with the Eco-Flex process is that it is inherently more expensive to produce as it requires a number of additional stages of production. First the aromatic polyester is created, second, the aliphatic polyester is created, and third the two elements are then partially cross-linked. The resultant material is inherently softer than traditional materials it is intended to replace and has significant stretch characteristics, even if the material is extruded as a significantly thicker film. The excessive stretch characteristics are generally undesirable in most plastics applications, thus, Eco-Flex materials are inappropriate for many, if not most plastic products. Last, the softness of the film makes the material difficult to extrude in thinner gauges, for example 50 microns up to 120 microns, therefore thicker gauges require substantially more material, which greatly increases raw material usage and cost. It goes without saying that increased raw material usage is counterproductive to improving its overall environmental footprint.
An attempt at a resin made from a renewable raw material comes from Brazil. The Braskem resins are made from sugar, which are completely polymerized such that the polyester they create is identical in properties to regular polyethylene, in other words, it degrades in 1000 years. The point of this resin is to avoid being captive to imported oil, to make it renewable although that is debatable. The main problem with Braskem's sugar-based polyester, in addition to the fact it is not considered degradable, is that it is limited to a raw material base of sugar, which is not plentiful in most parts of the world. The molecular structure tends to be very close to polyesters made from petroleum and shares similar characteristics of petroleum based polyesters, but their only environmental claim is renewability of its raw material feed stock, sugar. This claim for renewability, however, is partially offset by the greater energy requirements for the production. This is substantiated with a Life Cycle Analysis methodology that takes into account not only the raw material inputs (sugar) but also the fossil fuels and other forms of energy that are required for material conversion. Because of the requirement of these additional inputs for production, the product cannot claim to be made of renewable materials per se.
In addition to the Braskem and Eco-Flex resins, common additives made from cornstarch create a myriad of problems. These prior art technologies consist of Polyhydroxyalkanoate (PHA) and its related materials, PHB, PHBV, PHBHx, PHBO, PHBOd), and so on. These PHA-based materials carry brands such as Metabolix™ (PHB, PHBV) made by Metabolix/ADM, USA; Biopol™ (PHB, PHBV) made by Monsanto-Metabolix, USA; Enmat™ (PHB, PHBV) made by Tianan, China; Biocycle (PHB, PHBV) made by Copersucar, Brazil; Biomer L™ (PHB, PHBV) made by Biomer, Germany; and Nodax™ (PHBHx, PHBO, PHBOd) made by Procter & Gamble, USA.
PHA resins and its related materials are produced from specific starches that are corn derivatives. The typical starch base material is Amylopectin. In addition to inputs of specific starch materials, large inputs of water and electricity are required. The base material is converted metabolically by ingestion by genetically engineered microbes (also referred to as GMOs or “genetically modified organisms”), which consume the base material as a food source and excrete materials which can be polymerized after sufficient purification. A major problem with this process, unknown by many environmentalists, is that the extensive energy and water requirements are costly. Likewise, this process produces significant amounts of waste materials such as bio-mass of expended microbes that are wasted during production. The process is dependent on genetically modified organisms both on the production of base materials and on material conversion. Generally speaking this process increases energy requirements (usually from petroleum fired plants) since the corn must be processed, dried, and converted prior to conversion into resin.
While the use of GMOs is not restricted in the US, there is considerable concern worldwide about the proliferation of genetically modified crops with mainstream agricultural production. Europe has raised high levels of concern whereas the United States, driven by the economics and politics of agricultural concerns, has legislated few restrictions. While the potential dangers related to the use of GMOs are not presently available, the use of non-GMOs, would certainly represent a safe alternative. In some regions powerful consumer-groups are heavily advocating to ban all GMO crop-materials and promote only non-GMO crop materials.
The typical manufacturing process of PHAs includes: 1) Production of farm corn crops using standard, high volume crops, which crops are dependent on petroleum as raw material inputs in fertilizers and production machinery; 2) Drying and delivery of corn crops to a processor; 3) Grinding/milling, extraction of starches from the corn using substantial hot water solutions and complex, expensive, time-consuming purification methodologies; 4) Introduction of purified starches into bioreactor vats and inoculation with yeast, potentially dangerous e-coli or other GMO microbes, thus growing the microbes to target densities; 5) Purifying the excreted base materials by removal of the bio-mass and extraneous proteins, starches, plus a variety of other waste byproducts, and; 6) Polymerization of excreted base materials to produce resin suitable for manufacturing.
Another cornstarch based technology in addition to the PHA technologies are the prior art technologies referred to as Polylactic acid (PLA). Typical brands are Natureworks™ made by Cargill, USA; Lacty™ made by Shimadzu, Japan; Lacea™ made by Mitsui Chemicals, Japan; Heplon™ made by Chronopol, USA; CPLA™ made by Dainippon Ink & Chemical, Japan; Eco Plastic™ made by Toyota, Japan; PLA™ made by Galactic, Belgium; Treofan™ made by Treofan, Netherlands; L-PLA™ made by Purac, Netherland; Ecoloju™ made by Mitsubishi, Japan, and; Biomer L™ made by Biomer, Germany.
PLA resins, like its counterpart PHA, is typically made using the corn-derived starch with its base material Amylopectin. Like PHA, it also requires substantial water supplies and excessive energy in order to be produced. The base material is converted metabolically by ingestion by genetically engineered microbes which consume the base material as a food source and excrete materials which are then polymerized after sufficient purification. The energy intensive process produces substantial amounts of waste materials such as bio-mass of expended microbes. Like the PHA process, the PLA process is dependent on genetically modified organisms both on the production of base materials and on material conversion. The primary difference between PHA and PLA is that Lactic Acid is the byproduct used to produce PLA resin.
The typical manufacturing process of PLA includes the following steps: 1) Production of farm crops using standard, high volume corn crops, which crops are dependent on petroleum as raw material inputs in fertilizers and production machinery; 2) Drying and delivery of corn materials to a processor; 3) Grinding/milling, extraction of starches through hot water solutions and purification processes; 4) Introduction of purified starches into bioreactor vats and inoculation with yeast, potentially dangerous e-coli or other modified microbes, thus growing microbes to target densities; 5) Purification of excreted Lactic Acid by removal of bio-mass and extraneous proteins, starches, variety of other materials, and; 6) Polymerization of the excreted Lactic Acid to produce resin suitable for manufacturing.
The use of PHA and PLA resins in manufacturing film products, bags and so on have traditionally required gauges up to three times thicker than that of petroleum based products. In the film and bag making process, this equates to more costly extrusion outputs, slower conversion times, three times the storage space, three-fold shipping costs and so on. Thus, products made from these methodologies must be either those that require heavier gauges or where strength qualities are not important.
When products made from PLA and PHA resins are buried in a landfill or otherwise, they are consumed by a narrow range of bacteria, particularly ones that release protease enzymes. Thus, the question is raised of whether or not the environment in which they are buried is suitable for degradation.
Generally speaking, all cornstarch plastics tend to cause additional problems and expenses when extruded. This is primarily due to the fact that extruding a product three times thicker than a traditional plastic film requires more energy. The cornstarch based resin products are also more difficult to extrude with inferior bubble stability compared to traditional films. This results in the need to have a more highly controlled manufacturing environment and a higher waste output. Substantial know-how is required in order to adapt an extruder to extrude corn-based resins and produce films to convert into bags and so on. Likewise, conversion of cornstarch plastics is a slower process with more down time on conversion equipment in order to change roll stock and replace sealing components such as Teflon covers where residue tends to build up more quickly than traditional plastics. Thus, the overall end result with cornstarch-based plastic products is substantially higher costs, including energy to manufacture and ship. For example, the retail price of a common 33 gallon BioBag is about $0.85 to $0.95 per bag depending on quantity, whereas the price of a comparable bag made from regular polyethylene is about $0.09 to $0.15 each. The inherent cost of the product and its production processes has made market acceptance very limited. The minimum inputs in materials, energy for conversion through its various required stages of heat, fermentation, purification, and polymerization are costly, as is the infrastructure required to support it. The overall cost therefore is inherently too high for adequate marketability and penetration.
It is clearly understood in the industry of degradable plastics that the primary alternatives to petroleum based resins are dominated by corn, which conversion processes raise serious questions as to sustainability. Without question, the substantial increase in transportation, excess use of energy and water to convert and manufacture raise serious economic questions and new environmental questions altogether. The questions include the ability to consistently degrade, or perhaps if degradation even occurs. It is understandable that these methods are inadequate when addressing the true nature of environmentally sound plastics and their related products based on present costs, waste of energy, waste of precious water supplies, added transportation costs, the required use of petroleum products to produce and convert, let alone the questionable use of GMO microbes and their inherent waste.
The use of degradable starch-based film, bag, and other plastic products that overcome the numerous problems associated with prior art would be valuable to these trades and many others.